1. Technical Field
The present invention relates to liquid crystal display devices and electronic apparatuses.
2. Related Art
As one type of liquid crystal display device in which a liquid crystal layer is interposed between a substrate on the side of the viewer (first substrate) and a substrate on the side of the a source (second substrate), transflective liquid crystal display devices capable of functioning both in a reflective mode and in a transmissive mode have been known. For example, a transflective liquid crystal display device has been proposed in which a reflection film is provided on the inner surface of the substrate on the side of the light source, the reflective film being composed of a metal film made of aluminum or the like and provided with an opening, and the reflection film is allowed to act as a transflector. In the reflective mode, external light incident on the substrate on the side of the viewer passes through the liquid crystal layer, is reflected from the reflection film provided on the inner surface of the substrate on the side of the light source, passes through the liquid crystal layer again, and is then emitted from the substrate on the side of the viewer, thus displaying an image. On the other hand, in the transmissive mode, light from a light source incident on the substrate on the side of the light source enters the liquid crystal layer through the opening in the reflection film, passes through the liquid crystal layer, and is then emitted from the substrate on the side of the viewer toward the viewer, thus displaying an image. Consequently, in the reflection film formation region, a region provided with the opening corresponds to a transmissive display region, and the other region corresponds to a reflective display region.
However, the transflective liquid crystal display device according to the related art has a problem in that a viewing angle is narrow in transmissive display. The reason for this is that since the transflector is provided on the inner surface of the liquid crystal cell in order to prevent the generation of parallax, reflective display must be performed using only one polarizer provided on the side of the viewer, and thus freedom in optical design is limited. In order to overcome this problem, M. Jisaki et al. have proposed a novel liquid crystal display device using vertical alignment liquid crystal in “Development of transflective LCD for high contrast and wide viewing angle by using homeotropic alignment”, Asia Display/IDW'01, p. 133-136 (2001). This liquid crystal display device has the following three characteristics:
(1) A “vertical alignment (VA) mode” is employed in which liquid crystal having negative dielectric anisotropy is vertically aligned on a substrate, and the liquid crystal molecules are inclined by the application of a voltage.
(2) A “multigap structure” is employed in which the thickness (cell gap) of the liquid crystal layer in a transmissive display region is different from the thickness of the liquid crystal layer in a reflective display region, (refer to, for example, Japanese Unexamined Patent Application Publication No. 11-242226).
(3) A “multidomain alignment configuration” is employed in which the transmissive display region is divided into regular octagonal subdots, and a protrusion is formed at the center of each subdot in the transmissive display region on the substrate on the side of the viewer so that the liquid crystal molecules are radially inclined.
In the transflective liquid crystal display device, it is very effective to employ a multigap structure, as described in Japanese Unexamined Patent Application Publication No. 11-242226. The reason for this is that although incident light is transmitted through the liquid crystal layer only once in the transmissive display region, incident light is transmitted through the liquid crystal layer twice in the reflective display region, resulting in a difference in retardation (phase difference) between the transmissive display region and the reflective display region. By controlling the retardation by the multigap structure, the transmittance in the transmissive display region and the transmittance in the reflective display region are equalized, and thus a liquid crystal display device having excellent display quality can be obtained.
Furthermore, when the multidomain alignment configuration is not employed, liquid crystal molecules are inclined in random directions in the presence of an applied electric field, and discontinuous lines (disclinations) appear in the boundaries between the regions with different liquid crystal molecular orientations, resulting in a residual image or the like. Moreover, since the regions with different liquid crystal molecular orientations have different viewing angle characteristics, stain-like, rough unevenness may appear when viewed obliquely. In contrast, by employing the multidomain alignment configuration, it becomes possible to align the liquid crystal molecules in a predetermined direction in the presence of an applied electric field. Consequently, a liquid crystal display device having a wide viewing angle and excellent display quality can be obtained.
However, in a thickness adjustment layer for adjusting the thickness of the liquid crystal layer to produce the multigap structure, an inclined region is formed in the boundary between the transmissive display region and the reflective display region. In the inclined region, since liquid crystal molecules are aligned perpendicular to the alignment film provided on the surface, refractive index anisotropy is exhibited in a direction perpendicular to the substrate, resulting in a difference in retardation compared to other regions. As a result, in a black display, light leakage occurs in the inclined region, thus reducing the contrast.
In view of such a problem, according to Japanese Unexamined Patent Application Publication No. 11-242226, the inclined region of the thickness adjustment layer for adjusting the liquid crystal layer is covered with a reflection electrode composed of Al or the like to prevent light leakage in that region. However, when a connection between subdots is placed in the boundary between the transmissive display region and the reflective display region, it is not possible to cover the inclined region entirely with the reflection electrode, resulting in a reduction in contrast.